The officials say the New START treaty doesn't solve all nuclear issues between Moscow and Washington, but it would pay dividends by showing the United States' commitment.

Reporting from Washington — Senior Obama administration officials urged the Senate on Tuesday to swiftly ratify a new arms reduction treaty with Russia, arguing that it would improve ties with Moscow and build pressure on adversaries such as Iran and North Korea.

Secretary of State Hillary Rodham Clinton and Defense Secretary Robert M. Gates said that although the New START treaty did not solve all the nuclear issues between Moscow and Washington, it would pay dividends by convincing non-nuclear nations that the U.S. is committed to trimming its stockpile to reduce the world's nuclear dangers.

The treaty would reduce the ceiling on ready-to-use, long-range warheads from 2,200 to 1,550 and would authorize verification procedures to enable each country to keep an eye on the other's nuclear arsenal. The administration and its Senate allies, led by the Senate Foreign Relations Committee chairman, Sen. John F. Kerry (D-Mass.), are seeking swift approval of the treaty.

But Republican members signaled their skepticism. They argued Tuesday that, despite administration assertions to the contrary, the treaty could limit expansion of American missile defenses.

The Russians have threatened to withdraw from the treaty if the U.S. expands its systems, and Republicans fear that Obama will restrain missile defense development to avoid that outcome.